The use of DC motors to drive mechanisms is well known. For example, in an automotive application, DC motors are used to drive power window regulators or electronic throttle control (ETC) valves. It is also well known that, during the expected operation of motors in these applications, the motors can be required to overcome resistance imposed on the motors by the mechanisms themselves. Examples are resistance imposed on a window regulator motor by the compression of a window seal or resistance imposed on an ETC valve motor by the formation of ice around the throttle valve. With respect to an ETC valve, in extreme cold weather, during engine operation, ice can form in the air conduit upstream of the throttle valve. Then, when the engine is shut-down, engine heat can melt the ice allowing water to accumulate and freeze around the throttle valve. The formed ice can inhibit the throttle valve from being easily moved from the position it was left in at engine shut-down. Since a motor is used to control the rotational movement of the valve in an ETC system, the need to break the valve loose from an occasional ice obstruction as described puts added torque requirements on the motors used to drive the ETC valves.
As a result, current designs of ETC valves use larger motors than needed to rotate the valve under most conditions in order to be capable of generating the high torque needed for ice breaking. During normal operation, high motor torque is not required. Large motors compared to small motors have many disadvantages including higher costs, increased weight, and difficulties in packaging in the ETC.
It is an object of the present invention to provide a method and circuit used in conjunction with an electric motor that could provide a momentary increase in peak torque of the motor to overcome a resistance imposed on the motor.